Lift truck upright



United States Patent [72] Inventors Charles W. Conwell Portland, Oregon;Donald A. Harris, Vancouv er, Washington; Robert C. Shoemaker, Portland,Oregon [21] App1.No. 716,746 [22] Filed March 28, 1968 [45] Patented Nov24, 1970 [73] Assignee Hyster Company, Portland, Oregon a corporation ofNevada [54] LIFT TRUCK UPRIGl-lT 31 Claims, 5 Drawing Figs.

[52] U.S. Cl 92/146, 92/165;187/9,187/17 [51] Int. Cl F01bl/00, B66b9/20, B66b 11/09 [50] Field of Search 92/61,146, 51,52, 53, 150,8,-151;91/178,422,468; 137/216.01,216.2;187/9,17

[56] References Cited UNITED STATES PATENTS Re. 25.432 8/1963 Barnes92/51X Primary Examiner-Martin P. Schwadron Assista'm Examiner- LeslieJ. Payne Attarney- Buckhorn, Blore, Klarquist and Sparkman ABSTRACT: Alift truck with a four stage upright having a load carriage on the upperstage movable by a hydraulic cylinder on such stage. Another hydrauliccylinder on the lower stage extends and retracts the upright. A passagein the piston and piston rod of the upright cylinder conducts fluid froma source on the lift truck to the carriage cylinder without such fluidfirst passing through the cylinder cavity of the upright cylinder. Anadditional passage in such piston directs fluid into the cavity of theupright cylinder below the piston. The carriage cylinder operates undera lower pressure than the upright cylinder to elevate the carriagebefore the upright extends.

Pafiented Nov. 24, 1970 3,541,928

m 5/ \q 21 L as DONALD A. HARRIS ROBERT C. SHOEMAKER CHARLES W. CONWELLINVENTO/PS BUG/(HORN, BLORE, KLA/POU/ST 8 SPAR/(MAN ATTORNEYS PateniedNov. 24, 1970 Sheet BUG/(HORN, BLORE, KLAROU/ST 8 SPAR/(MAN ATTORNEYSLIFT-TRUCK UPRIGHT BACKGROUND OF THE INVENTION 1. Field of the InventionThe present invention relates to industrial lift trucks and moreparticularly to a lift truck having a multiple-stage upright withhydraulic means for raising a load carriage on the upper stage withoutextension of the upright stages.

2. Description of the Prior Art In the past, some lift trucks withmultiple stage uprights have incorporated a so-called free-lift cylinderon the upright for raising the load carriage on the upper stage of theupright while the upright remains fully retracted, thereby enabling useof the lift truck in places requiring low height clearances as well asin circumstances requiring the elevation of loads to great heightsattainable with the uprights fully extended. However, multiple-stagefree-lift uprights in the past have required the use of excessivelengths of exposed flexible hydraulic hose for supplying the free-liftcylinder with hydraulic fluid. This has presented a problem in reevingthe hose to avoid development of slack as the length of the upright isvaried and to protect the hose against rupture through external damage.

In attacking the foregoing hose problems and in attempting to simplifythe hydraulic circuitry required .to operate the cylinders in phase,attempts have been made to route hydraulic fluid through the hoistcylinder to the free-lift cylinder. However, these attempts have led topremature extension of the hoist cylinder and upright, thus defeatingthe purpose of the free-lift cylinder, without solving the hose problemsatisfactorily.

The foregoing problems'are most acute with respect to fourstage uprightsbecause of the great variation in distance between the source ofhydraulic fluid and the free-lift cylinder. As a result, the free-liftconcept has not been used extensively heretofore in conjunction withfour-stage uprights.

SUMMARY OF THE INVENTION The foregoing problems of the prior art areovercome by the resent invention through the provision of a multiplestage upright wherein pressure fluid is conducted from a source on thelift truck directly into the piston and piston rod of a hoist cylinderon the lower stage without first passing through the cavity of suchcylinder and then through a flexible hose extending from an upper end ofsuch piston rod to a free-lift cylinder on the upper stage. A passagewithin the piston of the hoist cylinder also directs a portion of theflow from the source into the hoist cylinder cavity below the piston. Apreloaded check valve in the piston passage leading to the hoistcylinder cavity helps prevent premature extension of the hoist cylinderand raising of the upright. Such check valve also prevents a sudden dropofthe extended upright in the event of rupture of the hose leading tothe free-lift cylinder, and serves to slow the descent of the pistonwithin the hoist cylinder as it approaches the bottom of the cylinderupon retraction of the uprights.

Primary objects of the invention are to provide:

1. A lift truck having an improved four-stage upright with a free-liftload carriage onits upper stage;

2. A multiple stage free-lift upright for a lift truck having animproved hoist cylinder with novel hydraulic circuitry for operating theload carriage independently of upright movement and without prematureextension of the upright;

3. An improved hydraulic phasing circuit for sequential operation of apair of hydraulic motors wherein one of the motors is a hydrauliccylinder;

4. An improved hoist cylinder for a multiple stage free-lift I uprightwith a novel hydraulic phasing circuitry built into the piston andpiston rod thereof for transmitting fluid pressure to the free-liftcylinder without appreciable pressure loss in the hoist cylinder toinsure raising of the freelift lift cylinder without premature extensionof the hoist cylinder;

5. An improved hoist cylinder for a multiple stage free-lift upright ofa lift truck which will not retract abruptly in the event of rupture ofthe hydraulic line from the hoist cylinder to the free-lift cylinderwhen the upright is extended;

6. An improved hoist cylinder for a multiple-stage upright with meansfor slowing the descent of the piston of such cylinder as it approachesthe bottom of the hoist cylinder cavity during retraction of theupright;

7. An improved hose reeving for a four-stage free lift upright of a lifttruck, such reeving requiring a minimum use of exposed hydraulic hoseand preventing the development of slack in the hose upon varying thelength of the upright; and

8. An improved four-stage free-lift upright for a lift truck havingsimplicity of design.

BRIEF DESCRIPTION OF THE DRAWINGS The foregoing and other objects andadvantages of the present invention will become more apparent fromthefollowing detailed description which proceeds with reference to theaccompanying drawings wherein:

FIG. 1 is a side elevational view of a lift truck incorporating afour-stage free-lift upright in accordance with the present invention,with the upright being shown in a fully retracted position;

FIG. 2 is a fragmentary side elevational view similar to that of FIG. 1showing the upright in a partially extended position;

FIG. 3 is a view similar to FIG. 2 showing the upright in a fullyextended position;

FIG. 4 is a schematic elevational view of the upright of FIG. 3 in itsfully extended position with portions broken away to reveal thefree-liftand hoist cylinders; and

FIG. 5 is a partial sectional view through the hoist cylinder on anenlarged scale and with the cylinder in its retracted position.

DETAILED DESCRIPTION General Assembly With reference to the drawings,FIGS. 1, 2 and 3 disclose an industrial lift truck 10 having afour-stage upright 12 mounted at its forward end for forwardly andrearwardly tilting movement through a hydraulically controlled linkage14. The fourstage upright includes a first, stationary lower stage 16,movable second and third stages 17, 18 and a movable upper stage 19.Upper stage 19 mounts a load carriage 21 including a load lifting fork22 for vertical movement thereon. The several stages, or sections, ofthe uprightare mounted for telescoping extension and retraction relativeto one another in any one of several manners well known in the art. Forexample, the uprights may be mounted in the manner shown in Shaffer U.S.Pat. No. 3,208,556 wherein each upright section includes a pair oflaterally spaced channel members within which the channel members of atelescopingly related upright section slide. Alternatively, the uprightsections may be mounted on rollers for movement relative to one anotherto reduce friction. I

Referring to FIG. 4, the four-stage upright includes a hydraulic poweredhoist cylinder 24 mounted on lower stage 16 and having an extensible rammeans including piston rod 26 connected at its upper end at 28 to secondstage 17 so that extension of the piston rod raises the second stagewith respect to the lower stage in a 1:1 ratio. A second hydrauliccylinder 30, the free-lift cylinder, is mounted on upper stage 19 andincludes an extensible piston rod 32 which supports at its upper endsheave means 34 about which a chain means 36 is trained. Chain 36 isconnected at one end to carriage 21 at 37 and at the otherend to thefree-lift cylinder casing at 38 so as to raise and lower the loadcarriage 21 on the upper stage in a 2:1 ratio with respect to movementof the free-lift cylinder. Because the free-lift cylinder is supportedon the upper stage and because its chain reeving 36 is not operativelyconnected to any other stage, the free-lift cylinder elevates and lowersthe load carriage without effecting any movement of the stages relativeto one another. This free-lift feature is most valuable in multiplestageuprights so that load fork 22 can raise and lower a load at low levelswith the uprights in a fully retracted position. This feature enablespassage of the lift truck through low doorways and its use in lowceilinged enclosures such as boxcars, while also enabling the handlingof loads at great heights when necessary.

Extension of hoist cylinder 24 effects an extension of the three movablestages 17, 18 and 19 simultaneously through a system of chain reevingbetween the stages. This reeving includes a first chain means 40 trainedabout sheave means 42 carried by the upper end of piston rod 26 of thehoist cylinder. Chain means 40 is fixed at one end at 44 to the casingof hoist cylinder 24 and at its opposite end at 46 to a lower portion ofthird stage 18, whereby the third stage 18 is moved at a ratio of 2:1with respect to the second stage 17 upon extension of the hoistcylinder. A second chain means 48 is trained about a sheave means 50near an upper end of third stage 18 and is connected at 51 to an upperend of second stage 17 and at 52 to a lower end portion ofupper stage19. Thus, upon extension of hoist cylinder 24, chain means 48 raisesupper stage 19 at a 2:1 ratio with respect to third stage 18, and at a3:1 ratio with respect to second stage 17.

Hydraulics Hoist cylinder 24 and free-lift cylinder 30 are hydraulicallyconnected so that the cylinders operate in sequence, with freeliftcylinder 30 extending first to raise load carriage 21 to the top of theupper stage, followed by extension of hoist cylinder 24 to extend thevarious upright stages simultaneously while the load carriage remains inits elevated position on the upper stage. The hydraulic circuitry isunique in that pressure fluid is conducted first through the piston andpiston rod of the hoist cylinder and then to the free-lift cylinder andcavity of the hoist cylinder with minimal pressure loss, with a minimaluse of hydraulic hose, and with a minimal differential in operatingpressures between the two cylinders.

Referring to FIGS. 4 and 5, a length of flexible hydraulic hose 54extends from a pump 56 on the lift truck to a fitting 58 at a lower sidewall of hoist cylinder casing 60. These elements define a fluid passagemeans referred to herein as the third fluid passage means. Fitting 58defines an inlet port 62 through the side wall of the casing throughwhich pressure fluid is led into a piston 64 when the piston is withinthe lower end of the cylinder casing. The piston is provided withinternal fluid passage means including a first inlet passage meansincluding a horizontal passage; portion 66 leading from an enlargedinlet cavity 68 at a cylindrical surface portion of the piston inregister-with inlet port 62 to a second, axial fluid passage means orportion 70 extending axially upwardly from passage 66 through piston 64.Axial piston passage 70 communicates at its upper end with an axialpassage 72 within piston rod 26 which terminates at an exit portoroutlet 74 at the upper end of the piston rod. A length of flexiblehose 76 extends from a fitting 78 connected to outlet 74 to thefree-lift cylinder 30. In doing so, hose 76 extends about a sheave'80 onthird stage 18 of the upright and thence upwardly to a fitting 32connected to an inlet ofthe free-lift cylinder 30. Sheave 80 isadjustable'vertically on the third stage to take up slaclt in hose 76when needed.

The first passage means also includes an axial lower passage portion 84which opens at 86 into the interior cavity 88 of cylinder casing 60 onthe pressure side of piston 64. A ball check valve 90 within pistonpassage 84 prevents the reverse flow of fluid from cylinder cavity 88through the passage into rod passage 72 leading to the free-liftcylinder and into inlet passage 66, for reasons which will'becomeapparent shortly. Check valve 90 also includes a preload spring 92 whichcloses the valve to fluid flow toward the lower pressure side of piston64 until a small predetermined fluid pressure of, say, about five to 10p.s.i. builds up in the piston passages. This feature helps prevent asurge of fluid pressure within cavity $8 and against piston 64 upon theinitial flow of fluid into the piston and rod passages to prevent anypremature extension of the upright.

Piston 64 includes a bypass orifice 9A which extends between cylinderpressure cavity 88 and inlet cavity 68 to bypass the check valve. Thisorifice allows a controlled bleeding of fluid from the pressure side ofpiston 6d and thus a slow, controlled descent of the piston and uprightfrom their extended positions in the event of a rupture of hydraulichose 76 leading to the free-lift cylinder. The orifice also operates inconjunction with the piston itself in slowing the descent of piston 64as it approaches the bottom of the cylinder casing during normalretraction of the extended cylinder to prevent damage to the cylindercasing and piston.

Operation Free-lift cylinder 30 is extensible under slightly lower fluidpressure than hoist cylinder 24 when the loading on both cylinders istaken into consideration. Thus, when pump 56 is activated with bothcylinders retracted to build up fluid pressure within the various fluidpassages, free-lift cylinder rod 32 extends first to its fully raisedposition to raise load carriage 23 before there is a sufficient buildupof fluid pressure within the pressure side ofthe hoist cylinder to raisepiston 64 and piston rod 26 to extend the upright. The capacity of pump56 is such that after free-lift cylinder is fully extended, fluidpressure continues to rise within the system to a level where the hoistcylinder can be fully extended. The differential between the operatingpressures of the two cylinders need only be slight, since the bypassingof hoist cylinder cavity 88 in directing fluid to the free-lift cylinderthrough the piston and piston rod of the hoist cylinder, preventspressure surges in the cavity 33 and thus premature extension of theupright and minimizes pressure losses in the hoist cylinder. Bymaintaining the operating pressure differential between the cylinderssmall, the upright can be extended immediately after the carriage hasbeen raised, without significantly changing the vertical speed of theload.

Referring to FIGS. 1, 2 and 3, FIG. 1 illustrates the initial fullyretracted position of the upright stages and load carriage when both thehoist cylinder and free-lift cylinder are fully retracted. The dashedline position of the carriage and fork 22 of FIG. 1 illustrates therelative positions of the upright stages and carriage with the free-liftcylinder fully extended and the hoist cylinder still fully retracted.FIG. 2 illustrates the partially extended upright stages upon partialextension of the hoist cylinder. The free-lift cylinder remains fullyextended to maintain the carriage in its elevated position on the upperstage. In FIG. 3, hoist cylinder rod 26 has become fully extended, andthus the upright too is extended fully, with the load carriage remainingin its fully raised position on the upper stage. The FIG. 3 position ofthe carriage and upright represents the greatest height to which a loadcan be raised by the lift truck.

From FIG. 5 it will be apparent that after the free-lift cylinder hasbeen extended and piston 64 rises an initial distance from the bottom ofcylinder casing 60, pressure fluid will ceaseentering the cylinderthrough inlet cavity 68 and piston passage 66 and instead will flowdirectly into the pressure side of the cylinder cavity 86 below thepiston to continue raising the piston. The enlarged shape of pistoninlet cavity 623 and the short distance between its lower extremity andthe bottom of piston 64 insures that there will be no interruption inthe buildup of fluid pressure against the bottom of the piston as thepiston rises past the inlet port 62.

When lowering a load on fork 22 from a fully extended position of theupright, the direction of fluid flow through inlet port 62 is reversedso that it becomes the fluid outlet. Because of the higher pressurenecessary to extend the hoist cylinder than the free-lift cylinder, areduction in fluid pressure retracts the hoist cylinder and thus theupright before the free-lift cylinder retracts to lower the loadcarriage on the fourth stage.

During the descent of piston 64 within cylinder casing 60, check valve90 closes, and the piston forces fluid out of the lower end of thecasing through outlet port 62. However as piston 64 nears the bottom ofthe casing, the piston itself slides over port 62, cutting off fluidflow directly from the cylinder cavity to the port. Check valve 90 alsoprevents flow from the cylinder cavity through the internal pistonpassages 84 and 66 to port 62. Thus, the descent of the piston slows asit approaches the bottom of the casing and finally bottoms only as fastas fluid can bleed from the cylinder cavity below the piston throughorifice 94. This self-cushioning effect of the piston prevents cylinderand piston damage which might otherwise result from a rapid, uncheckedpiston descent.

The check valve and orifice also prevent the same sort of damage in theevent of rupture of hose 76 to the free-lift cylinder should it breakwhile the upright and carriage are extended and under heavy load. insuch circumstances, the resulting pressure drop would not cause a rapiddescent of piston 64 since fluid below such piston could only bleedslowly to the hose break through orifice 94, and thus the piston androd, and the upright, would descend slowly.

Having illustrated and described a preferred embodiment of my inventionit should be apparent to those skilled in the art that the same permitsof modification in arrangement and detail.

lclaim:

1. Pressure fluid-actuated means for use with an extensible multistagemast or boom apparatus including:

a first fluid motor for mounting on one stage of said apparatus;

a second fluid motor separated from said first fluid motor for mountingon another stage of said apparatus;

at least one of said motors comprising a fluid cylinder means includinga casing, and an extensible ram means within said casing and capable ofextension outside said casing, said ram means having a fluid exit portin an outer portion thereof outside said casing;

a source of pressure fluid;

first fluid passage means within said ram means communicating with theinterior of said cylinder means on a pres sure side of said ram means;

second fluid passage means within said extensible ram meansinterconnecting said first fluid passage means and said exit port;flexible hose means interconnecting said exit port and said second fluidmotor means; and

third fluid passage means extending through said casing for connectingsaid source to said first fluid passage means in a predeterminedposition of said ram means wherein pressure fluid enters said firstfluid passage means from said source before passing to the pressure sideof said ram means.

2. Apparatus according to claim 1 wherein said first fluid passage meansincludes a pressure fluid inlet on a side of said ram means in slidingengagement with a wall of said-cylinder means, and said third fluidpassage means includes a fluid inlet port means in said wall and inregistration with said pressure fluid inlet of said ram means in saidpredetermined position of said ram means.

3. Apparatus according to claim 2 wherein said first passage meansincludes a first fluid outlet opening to the pressure side of said ramand a second fluid pressure outlet connected to said second passagemeans.

4. Apparatus according to claim 1 including one-way valve means in saidfirst passage means permitting fluid flow from said source to said otherfluid motor means and to the pressure side ofsaid ram means butpreventing fluid flow from the pressure side of said ram means throughsaid valve means to said second and third passage means. Y

5. Apparatus according to claim 4 wherein said one-way valve meansincludes means preloading said valve means in a direction to permitfluid flow to the pressure side of said ram means only when said fluidexceeds a predetermined pressure.

6. Apparatus according to claim 4 including restricted fluid passagemeans bypassing said one-way valve means and connecting the-pressureside of said ram means with said first passage means at a positionbetween said third passage means and said valve means.

7. Apparatus according to claim 1 wherein said first passage meansincludes a first passage portion within said ram means connected to saidsecond passage means and a second passage portion in parallel with saidfirst passage portion communicating with the pressure side of said rammeans, and orifice means within said ram means connecting said firstpassage means to the pressure side of said ram means in parallel withsaid second passage portion.

8. Apparatus according to claim 2 wherein said cylinder means comprisesa one-way hoist cylinder with said inlet port serving as a fluid outletfrom said cylinder upon retraction of said ram means from an extendedposition, and one-way valve means in said first passage means permittingfluid flow through said first passage means to the pressure side of saidram means but preventing fluid discharge from said pressure side throughsaid first passage means to said inlet port, so that upon retraction ofsaid ram means said ram means blocks the discharge of fluid from saidpressure side to said inlet port when said ram means approaches itsfully retracted position.

9. Apparatus according to claim 8 including orifice means bypassing saidvalve means and interconnecting said pressure side of said ram means andsaid inlet port when said ram is in blocking relation to said inletport, so as to permit a slowed movement of said ram means to a fullyretracted position when said ram means approachessaid retractedposition.

10. Apparatus according to claim 1 wherein said cylinder means and saidother fluid motor means are sized so that one of said fluid motor meansis operable under a lower fluid pressure than the other said fluid motormeans whereby said two motor means will operate in sequence.

11. Apparatus according to claim 1 wherein said other fluid motor meanscomprises a second fluid cylinder means having a second ram means and isoperable under a lower fluid pressure than the ram means of saidfirst-mentioned cylinder means so that said second ram means will extendbefore the extension of the ram means of said first cylinder means.

12. Apparatus according to claim 11 wherein said first and second fluidcylinder means comprise hoist cylinders in a lift truck having atelescoping multiple stage upright means with a load carriage movable onan upper stage of said upright means, said first cylinder means beingoperable to extend and retract the stages of said upright means and saidsecond cylinder means being operable to move said load carriagevertically on said upper stage.

13. Apparatus according to claim 12 wherein said first cylinder means isconnected to a lowermost stage of said upright means and said secondcylinder means is carries by said upper stage. 7

14. Apparatus according to claim 13 wherein said upright means includesfour stages including a fixed lower stage and three movable stages, withsaid stages being interconnected so that upon pressure fluid from saidsource entering said first cylinder means, first said load carriage iselevated to the upper end of said upper stage through extension of saidsecond generally axially extending fluid passage means within saidpiston portion and said rod means and having a first fluid outlet in anouter end portion of said rod means outside said casing and a secondfluid outlet opening into said cylinder casing on a pressure side ofsaid piston portion;

lateral fluid passage means within said piston portion extending from afluid-inlet at a surface portion of said piston into communication withsaid axial passage means at a position between said fluid outlets; and

fluid inlet port means in said casing in registration with said fluidinlet in said piston at a predetermined position of said piston withinsaid casing.

16. Apparatus according to claim including check valve means within saidaxial passage means between said second outlet and said lateral passagemeans restricting fluid flow from the interior of said casing tosaidlateral passage means and said first outlet.

17. Apparatus according to claim 16 including orifice means within saidpiston bypassing said check valve means and connecting said interiorportion of said casing with said fluid inlet port means.

18. Apparatus according to claim 16 wherein said check valve meansincludes means closing said valve means to flow in a direction towardthe interior of said casing and operable under a predetermined fluidpressure to open said valve means to fluid flow in said direction.

19. In a lift truck having an upright with multiple-telescoping stagesincluding:

a lower stage, an upper stage and at least one intermediate stage, witha load carriage movable vertically along said upper stage;

a first extensible power cylinder means on said upper stage for movingsaid load carriage;

a second extensible power cylinder means on one of said stages otherthan said upper stage for extending and retracting said stages;

said second power cylinder means including a cylinder cavity and anextensible ram means slidable within said cavity; and

fluid passage means including passage means extending through said rammeans and from an outlet port of said ram means to said first powercylinder means for directing fluid from a source of pressure fluid onsaid'lift truck through said ram means and to said first power cylindermeans without said fluid first passing into said cylinder cavity on apressure side of said ram means when said ram means is retracted.

20. Apparatus according to claim 19 wherein said second cylinder meansis on said lower stage.

21. Apparatus according to claim 19 wherein there are four of saidstages and said second cylinder means is on said lower stage.

22. Apparatus according to claim 19 wherein said fluid passage meansincludes an inlet passage portion extending from said source into theinterior of said ram means, a first branch passage portion extendingfrom said inlet passage portion within said ram means to said outletport, a flexible passage portion extending from said outlet port to saidfirst cylinder means, and a second branch passage portion extending fromsaid inlet passage portion within said ram means to said cylinder cavityofsaid second cylinder means.

23. Apparatus according to claim 22 including check valve meansrestricting fluid flow from said cylinder cavity through the fluidpassage portions within said ram means.

24-. Apparatus according to claim 22 wherein said first cylinder meansis extensible under a lower fluid pressure than said second cylindermeans.

25.1n a lift truck, an upright comprising:

four telescoping sections, including a first lower section,

second and third intermediate sections and a fourth upper section;

a load carriage movable vertically on said upper section, a

first hydraulic cylinder means interconnecting said first and secondsection; a second hydraulic cylinder means on said upper section forraising and lowering said load carriage on said upper section;

fluid passage means within a piston rod portion of said first cylindermeans for conducting pressure fluid from a source on said truck to saidsecond cylinder means; and flexible hose means interconnecting saidfluid passage means and said second cylinder means.

26. Apparatus according to claim 25 wherein said hose means extends froman upper portion of said piston rod, about a sheave means on said thirdsection and thence to a fluid inlet port on said second cylinder means.

27. Apparatus according to claim 26 wherein said sheave means isvertically adjustable on said third section to take up slack in saidhose means.

28. In a multiple-stage extensible mast or boom apparatus;

a first fluid motor on one stage of said apparatus;

a second fluid motor separated from said first fluid motor on anotherstage of said apparatus;

said second fluid motor comprising an extensible fluid cylinder meansfor extending and retracting said multiple stage apparatus;

said cylinder means including a cylinder casing defining a cylindercavity and an extensible ram means movable within said cavity andoutwardly of an open end of said casing; fluid passage means extendingfrom a source of pressure fluid outside said casing to an inlet port insaid casing;

ram fluid passage means extending within said ram means and including aninlet opening in communication with said inlet port in a retractedposition of said ram means, a first outlet port at an outer end of saidram means, and a second outlet port at an inner end of said ram meansopening into said cylinder cavity; and

flexible fluid passage means operably interconnecting said first outletport of said ram means and said first fluid motor so that the pressureside of said ram means and said first fluid motor are connected inparallel to said source through said ram means.

29. Apparatus according to claim 28 wherein said first fluid motor isoperable under a lower fluid pressure than said second fluid motorwhereby the arrangement of said passage means inhibits prematureextension of said cylinder means.

30. Apparatus according to claim 28 including one-way valve means withinsaid ram passage means restricting fluid flow from said cavity to saidinlet and outlet ports.

31. Apparatus according to claim 30 wherein said valve means includesfluid pressure sensitive means preventing fluid flow through said valvemeans to said cylinder cavity until there is a predetermined fluidpressure buildup within said ram passage means.

